In a medium bowl, combine the flour, baking powder, baking soda, and salt. Set aside.
Brown the butter: In a small saucepan, add 170g (12 tbsp) butter and place over medium heat. As the butter melts, stir it with a rubber spatula to encourage even cooking. Once the butter has fully melted, it will alternate between rapid large bubbles and gentle small foamy bubbles. The butter will be ready once it turns a dark golden color and the fat solids have darkened and settled at the bottom of the pan.
In a large bowl, weigh the brown butter out to 140g (½ cup + 2 tbsp) and allow to cool for a few minutes.
Once the brown butter is cool, add the brown sugar and malted milk powder and whisk together vigorously until fully combined. Whisk in the egg and vanilla until smooth.
Fold in the dry ingredients with a rubber spatula until mostly combined, then fold in the chocolate chips until evenly dispersed.
Using a 2 tablespoon cookie scoop, portion the cookie dough onto a baking sheet. Roll two cookie dough balls together to create 4 tablespoon cookie dough balls. Pull a few chocolate chips to the top if desired.
Wrap the baking sheet with plastic wrap and chill in the fridge overnight or up to 48 hours.
When you're ready to bake the cookies, preheat the oven to 350 degrees and line two large baking sheets with plastic wrap.
Place the cookie dough on the baking sheets spaced two inches apart. Re-roll the cookie dough in your hands if necessary.
Bake the cookies for about 12 minutes until just barely golden on the edges.
Once the cookies come out of the oven, immediately use a round cookie cutter or glass to scoot the edges in and make them perfectly round.
Allow to cool for a few minutes on the baking sheet, and enjoy!